[v6.6] KASAN: use-after-free Read in ocfs2_claim_suballoc_bits

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3a8ababb8b6a Linux 6.6.101
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=135d0042580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a2bd95b6de4839b7
dashboard link: https://syzkaller.appspot.com/bug?extid=7ba90879bba025f88941
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f06c672f5fa8/disk-3a8ababb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9af9b7afcdc5/vmlinux-3a8ababb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/351a55aafa77/bzImage-3a8ababb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7ba908...@syzkaller.appspotmail.com

loop2: detected capacity change from 0 to 32768
ocfs2: Mounting device (7,2) on (node local, slot 0) with ordered data mode.
==================================================================
BUG: KASAN: use-after-free in ocfs2_find_victim_chain fs/ocfs2/suballoc.c:1391 [inline]
BUG: KASAN: use-after-free in ocfs2_claim_suballoc_bits+0xeb0/0x2230 fs/ocfs2/suballoc.c:1927
Read of size 4 at addr ffff88805836e000 by task syz.2.1611/12219

CPU: 1 PID: 12219 Comm: syz.2.1611 Not tainted 6.6.101-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
<TASK>
dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xac/0x220 mm/kasan/report.c:468
kasan_report+0x117/0x150 mm/kasan/report.c:581
ocfs2_find_victim_chain fs/ocfs2/suballoc.c:1391 [inline]
ocfs2_claim_suballoc_bits+0xeb0/0x2230 fs/ocfs2/suballoc.c:1927
ocfs2_claim_new_inode+0x32a/0x780 fs/ocfs2/suballoc.c:2210
ocfs2_mknod_locked+0x101/0x250 fs/ocfs2/namei.c:635
ocfs2_mknod+0x107e/0x20f0 fs/ocfs2/namei.c:381
ocfs2_create+0x196/0x410 fs/ocfs2/namei.c:674
lookup_open fs/namei.c:3488 [inline]
open_last_lookups fs/namei.c:3556 [inline]
path_openat+0x1277/0x3190 fs/namei.c:3786
do_filp_open+0x1c5/0x3d0 fs/namei.c:3816
do_sys_openat2+0x12c/0x1c0 fs/open.c:1419
do_sys_open fs/open.c:1434 [inline]
__do_sys_creat fs/open.c:1512 [inline]
__se_sys_creat fs/open.c:1506 [inline]
__x64_sys_creat+0x90/0xb0 fs/open.c:1506
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fbe78b8eb69
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fbe799e0038 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 00007fbe78db5fa0 RCX: 00007fbe78b8eb69
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000d80
RBP: 00007fbe78c11df1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fbe78db5fa0 R15: 00007ffd932b07d8
</TASK>

The buggy address belongs to the physical page:
page:ffffea000160db80 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x5836e
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000000 ffffea000160dbc8 ffffea0001555c48 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 12196, tgid 12156 (syz.5.1595), ts 651702874283, free_ts 654247976960
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
prep_new_page mm/page_alloc.c:1561 [inline]
get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
__alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
__folio_alloc+0x10/0x20 mm/page_alloc.c:4489
vma_alloc_folio+0x47a/0x8f0 mm/mempolicy.c:2242
shmem_alloc_folio+0x179/0x230 mm/shmem.c:1680
shmem_alloc_and_acct_folio+0x189/0x630 mm/shmem.c:1705
shmem_get_folio_gfp+0xcde/0x2ac0 mm/shmem.c:2042
shmem_fault+0x1b6/0x7f0 mm/shmem.c:2249
__do_fault+0x13b/0x4e0 mm/memory.c:4243
do_read_fault mm/memory.c:4616 [inline]
do_fault mm/memory.c:4753 [inline]
do_pte_missing mm/memory.c:3688 [inline]
handle_pte_fault mm/memory.c:5025 [inline]
__handle_mm_fault mm/memory.c:5166 [inline]
handle_mm_fault+0x3886/0x4920 mm/memory.c:5331
faultin_page mm/gup.c:868 [inline]
__get_user_pages+0x5ea/0x1470 mm/gup.c:1167
populate_vma_page_range+0x2b6/0x370 mm/gup.c:1593
__mm_populate+0x24c/0x380 mm/gup.c:1696
mm_populate include/linux/mm.h:3317 [inline]
vm_mmap_pgoff+0x2e7/0x400 mm/util.c:561
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1154 [inline]
free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2475
release_pages+0x1fa0/0x2220 mm/swap.c:1022
__folio_batch_release+0x71/0xe0 mm/swap.c:1042
folio_batch_release include/linux/pagevec.h:83 [inline]
shmem_undo_range+0x5d0/0x1a40 mm/shmem.c:1027
shmem_truncate_range mm/shmem.c:1136 [inline]
shmem_evict_inode+0x273/0xa70 mm/shmem.c:1265
evict+0x486/0x870 fs/inode.c:705
__dentry_kill+0x431/0x650 fs/dcache.c:611
dentry_kill+0xb8/0x290 fs/dcache.c:-1
dput+0xfe/0x1e0 fs/dcache.c:918
__fput+0x5e5/0x970 fs/file_table.c:392
task_work_run+0x1ce/0x250 kernel/task_work.c:239
exit_task_work include/linux/task_work.h:43 [inline]
do_exit+0x90b/0x23c0 kernel/exit.c:883
do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
get_signal+0x12fc/0x1400 kernel/signal.c:2902
arch_do_signal_or_restart+0x96/0x780 arch/x86/kernel/signal.c:310

Memory state around the buggy address:
ffff88805836df00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88805836df80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88805836e000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88805836e080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88805836e100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 3a8ababb8b6a Linux 6.6.101
git tree: linux-6.6.y

console output: https://syzkaller.appspot.com/x/log.txt?x=101b5aa2580000

kernel config: https://syzkaller.appspot.com/x/.config?x=a2bd95b6de4839b7
dashboard link: https://syzkaller.appspot.com/bug?extid=7ba90879bba025f88941
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15d77834580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15177cf0580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f06c672f5fa8/disk-3a8ababb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9af9b7afcdc5/vmlinux-3a8ababb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/351a55aafa77/bzImage-3a8ababb.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/355942972ec4/mount_0.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=1579caa2580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7ba908...@syzkaller.appspotmail.com

ocfs2: Mounting device (7,1) on (node local, slot 0) with ordered data mode.

==================================================================
BUG: KASAN: use-after-free in ocfs2_find_victim_chain fs/ocfs2/suballoc.c:1391 [inline]
BUG: KASAN: use-after-free in ocfs2_claim_suballoc_bits+0xeb0/0x2230 fs/ocfs2/suballoc.c:1927

Read of size 4 at addr ffff88807b30f000 by task syz.1.18/5967

CPU: 0 PID: 5967 Comm: syz.1.18 Not tainted 6.6.101-syzkaller #0

RIP: 0033:0x7fb4d6f8eb69

Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007fff2caac8e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 00007fb4d71b5fa0 RCX: 00007fb4d6f8eb69

RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000d80

RBP: 00007fb4d7011df1 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007fb4d71b5fa0 R14: 00007fb4d71b5fa0 R15: 0000000000000002

</TASK>

The buggy address belongs to the physical page:

page:ffffea0001ecc3c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b30f

flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()

raw: 00fff00000000000 ffffea000096a248 ffffea000094e688 0000000000000000
raw: 0000000000000000 0000000000120000 00000000ffffffff 0000000000000000

page dumped because: kasan: bad access detected
page_owner tracks the page as freed

page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 5766, tgid 5766 (sshd-session), ts 55756903408, free_ts 82015757291

set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
prep_new_page mm/page_alloc.c:1561 [inline]
get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
__alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457

alloc_slab_page+0x5d/0x170 mm/slub.c:1876
allocate_slab mm/slub.c:2023 [inline]
new_slab+0x87/0x2e0 mm/slub.c:2076
___slab_alloc+0xc6d/0x12f0 mm/slub.c:3230
__slab_alloc mm/slub.c:3329 [inline]
__slab_alloc_node mm/slub.c:3382 [inline]
slab_alloc_node mm/slub.c:3475 [inline]
slab_alloc mm/slub.c:3493 [inline]
__kmem_cache_alloc_lru mm/slub.c:3500 [inline]
kmem_cache_alloc+0x1b7/0x2e0 mm/slub.c:3509
vma_lock_alloc kernel/fork.c:460 [inline]
vm_area_dup+0x61/0x270 kernel/fork.c:513
__split_vma+0x19f/0xc00 mm/mmap.c:2369
do_vmi_align_munmap+0x2dc/0x1660 mm/mmap.c:2497
do_vmi_munmap+0x252/0x2d0 mm/mmap.c:2656
__vm_munmap+0x193/0x3c0 mm/mmap.c:2957
__do_sys_munmap mm/mmap.c:2974 [inline]
__se_sys_munmap mm/mmap.c:2971 [inline]
__x64_sys_munmap+0x60/0x70 mm/mmap.c:2971

do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1154 [inline]
free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336

free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
discard_slab mm/slub.c:2122 [inline]
__unfreeze_partials+0x1cf/0x210 mm/slub.c:2662
put_cpu_partial+0x17c/0x250 mm/slub.c:2738
__slab_free+0x31d/0x410 mm/slub.c:3686
qlink_free mm/kasan/quarantine.c:166 [inline]
qlist_free_all+0x75/0xe0 mm/kasan/quarantine.c:185
kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:305
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
slab_alloc_node mm/slub.c:3485 [inline]
kmem_cache_alloc_node+0x150/0x330 mm/slub.c:3530
__alloc_skb+0x108/0x2c0 net/core/skbuff.c:640
alloc_skb include/linux/skbuff.h:1284 [inline]
nlmsg_new include/net/netlink.h:999 [inline]
rtmsg_ifinfo_build_skb+0x8c/0x260 net/core/rtnetlink.c:4063
rtmsg_ifinfo_event net/core/rtnetlink.c:4106 [inline]
rtmsg_ifinfo+0x8c/0x1a0 net/core/rtnetlink.c:4115
netdev_state_change+0xf0/0x150 net/core/dev.c:1410
linkwatch_do_dev+0x10d/0x160 net/core/link_watch.c:191
__linkwatch_run_queue+0x40f/0x660 net/core/link_watch.c:244

Memory state around the buggy address:

ffff88807b30ef00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88807b30ef80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88807b30f000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88807b30f080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88807b30f100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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